Theoretical model for a nonequilibrium helium arc plasma

Abstract

A semiempirical model for a nonequilibrium helium arc plasma is used to interpret systematic deviations in existing spectroscopic data and to aid in computing nonequilibrium plasma transport properties. Two groups of bound electronic states are assumed to exist which follow Boltzmann distributions at T e (upper states) and T R ≠ T e (lower states). Under certain conditions, T R can be interpreted as a radiation temperature characterizing the optically thick part of the spectrum and can be calculated using a restricted Rosseland approximation. The nonequilibrium plasma is characterized by electron densities as much as several orders of magnitude greater than the local thermodynamic equilibrium value. The model reproduces the experimental data in detail once the electron temperature profile is given.